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My Stealth Recording Kit: How I Record Audio Without Being Seen…

June 19, 2016

My Stealth Recording Kit: How I Record Audio Without Being Seen…

When I first saw Slumdog Millionaire by Danny Boyle, I was instantly impressed with the naturalness that appeared to distinguish this film from many others. I started searching for information about this movie and found that most of the public scenes were shot on hidden cameras to avoid detection.

This got me thinking and led me on some crazy adventures of my own… And speaking from experience, I know people don’t always respond well to a person with a microphone, windshield zeppelin, or a device with glowing lights. 🙂 It is expected that you may receive excessive interest in what you are doing, either by members of the public, or by police officers. If you are looking a bit suspicious, such as digging in a bag filled with wires and devices, or holding a zeppelin that resembles a fully automatic weapon, you will have some seriously hard times… I am sure some of you have experienced this already. Play it cool. 🙂

Setting a task: we want to record natural atmospheres without attracting attention from the crowd or police, to quickly set up our equipment and to achieve this with the highest recording quality possible.

Not an easy task. But don’t despair, there’s always a way! What’s the solution? A stealth field recording using miniature microphones and a compact audio recorder.

The goal is obvious, therefore, we must start the selection of equipment and its stealth placement. First of all, we must choose the microphones type. Unfortunately, we can’t use bulky mics with large diaphragms (LDC) because of their large dimensions that will attract attention. Therefore, we will focus on mics that can be mounted on our body, bags, backpacks or clothing. Of course those are lavalier, omnidirectional microphones and their selection is huge. There are cheap and low quality mics and quite expensive and very high quality models. My choice fell on the Danish microphone company DPA (which has some legacy of Brüel & Kjær) and their 4060 model. These microphones are the industry standard among sound designers, as they have a very good performance for such a small size. They have nice low and high frequency responses and fairly good linearity across the whole spectrum.

The payback for the small size is the relatively high noise level, which is a common characteristic for many lavalier mics. In the case of DPA 4060 it is 23-26 dB of (A-weighted) noise. But I believe that this is nothing compared to the audio quality and miniature size.
In any case, keep in mind, that lavalier mic is not a magic thing and will not give you the quality and presence, that LDC microphones are providing. It’s still a compromise between physical size, audio quality and noise, therefore: carefully choose the models of lavaliere microphones.

Next, we need some kind of wind protection, though omnidirectional microphones are less affected by the wind than other types condenser mics, but it’s still a vital part of our kit. My choice fell on well known company Rycote and its Lavaliere Windjammers, but unfortunately, in the end it was a mistake.

Don’t get me wrong: Rycote is a highly respected company with great products, but their windscreens for lavalier microphones suffered from several problems: large size, poor protection from strong wind gusts and muddy sounding. The problem is that Lavaliere Windjammers are using foam inserts, attaching on top of the mics and only then we are putting on muff wind protection. Of course, this is the way that Rycote is achieving maximum compatibility with almost all lavalier mics on the market. So, for example, if you have several different models of lavs in your sound recoding kit – you may think about Lavaliere Windjammers. But for our task this creates a problem: there is no dead air bubble inside, which is better at extinguishing wind gusts and improving sound transparency of the windscreen.
In the end, I abandoned the Rycotes and tried another product: the Windbubbles from Bumblebee Industries, which worked much better, because of the air bubble inside. It was smaller and there were no foam inserts. Unfortunately, in the case of Windbubbles you need to pick them accordingly to a size of your microphones: they are not universal as Rycote products.

The next step is a choice of audio recorder. This is also a very important part of our kit: the recorder should be compact (so it can be hidden in a small bag or even inside of our clothing), it must provide high-quality sound recording, the controls must be easily accessible and menu-diving should be absent or kept to a minimum. It’s also desirable to have remote controls over rec start and stop, for example using a smartphone. My choice fell on a MixPre-D field sound mixer by Sound Devices. It meets all the requirements: it has great sound, analog limiters, smartphone (or tablet) connectivity via USB and can work as a class-compliant audio interface. This USB connection allows us to use phone or tablet as a bit-bucket with MixPre-D’s built-in analog-to-digital converters.

You only need to set up levels on the mixer itself and then you can start or stop recording directly from your phone or tablet. This allows us to not stand out from the crowd: now you are just ordinary person who types something into his (or her) smartphone or tablet. The USB cable, sticking out from your device looks like a charging wire from a power bank.

The choice of monitor headphones is completely dependent on your personal preferences. Due to their look, even the most biggest, can pass a trendy fashion acessory.

Now the final stage: how to put all this stuff on our clothes?

First we will attach the mics themselves: I use two types of attaching: on hat (or baseball cap) and on the bag. If you don’t mind that people (especially children) will sometimes smile, looking at funny fur pompons on your cap or bag – there will be no other problems. I’m using standard lavaliere mic clips for mounting microphones on clothing. When worn on a cap or hat, we get a pseudo-binaural type of recording, which is not always the best option for a correct stereo image. It’s because of our head, that will affect on how microphones will perceive certain frequencies. Due to the fact, that our head partly blocks mid and high frequencies, but does not affect on lows, this can lead to some problems in stereo image when playing back on studio monitors. For better understanding what binaural recording is you should check out some specialized literature. But the advantages of this attachment is that our mics are always located above the crowd and this allows us to make the atmosphere more open and without risk of our microphones getting hit by people walking past.

The second type of attachment is on straps of a bag. This is closer to A-B stereo, which provides more correct playback on studio monitors and has wider stereo image. The disadvantages of this mounting is that if are in a heavy crowd – there is a significant chance that our recording will become muffled with excessive activity from all directions and will become very claustrophobic. Also, our microphones can be hit by passing pedestrians and there is a chance that you will record more reflections from the asphalt. It should be obvious that the type of mic attachment is highly dependent on the task and environmental conditions.

Now we need to hide the recorder. If you wear a wide coat, you can try to secure the recorder under your clothes in a kangaroo-bag. It’s a very comfortable placement, doesn’t restrict arm movement and keeps the recorder warm from your body, which positively affects on battery life.

The second option is to carry recorder in an inconspicuous shoulder bag, that in combination with mic mounting on bag straps makes it very comfortable to place the entire kit in one place.

Next, we need to connect the USB port of our recorder to a phone/tablet using an OTG cable (Android) or Apple Camera Connection Kit (iPhone and iPad) and to use an app to record sounds directly to our smartphone. I’m using my Android phone with the “USB Audio Recorder Pro” app.

Now, we need to hide and secure all wires under our clothes and to provide some protection to mic connectors (I use DIY design, made of plastic tubes, because there is a significant chance to break pretty fargile MicroDot connectors on DPA mics when you are moving).

So, our kit for stealth recording is now ready! It provides decent quality and low visibility, which allow us to be in the center of any event without the risk of being noticed.

I hope this article was useful for people who want to join the world of stealth field recordings. Try not to get caught! 🙂

About Igor Tikhonov

Comments

Nice article Igor. I too own a pair of the DPA 4060s along with my SD MixPre-D fed into Zoom H4. My setup is a bit more bulkier than yours but I tend to get away unnoticed while recording the many activities of my city of San Francisco. Thanks for the useful info, I’d like to slim down my stealth setup.

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